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D-Dimer
D-Dimers are fibrin degradation products formed as a result of fibrinolysis or clot degradation by plasmin. Although plasmin cleaves fibrinogen, fibrin, and cross-linked fibrin during fibrinolysis, only the degradation of cross-linked fibrin, formed during active coagulation, results in D-Dimer formation. This fibrin-derived peptide can therefore be used as an effective biomarker to identify active coagulation and fibrinolysis.
Background1
The D-Dimer assay is now preferred in the evaluation and management of deep-vein thrombosis (DVT), a manifestation of thromboembolism, over conventional diagnostic tools due to its specificity and non-invasive nature.
Clinical Applications
As a biomarker, the D-Dimer assay provides critical diagnostic inputs to the clinician in the diagnosis and management of thromboembolism. Evaluation of D-Dimer levels is carried out in conjunction with the clinical probability of thromboembolism, as specified by Wells, et al. (2007).
- Patients suspected of thromboembolism demonstrate significantly elevated levels of D-Dimer.
- Despite its high sensitivity, D-Dimer is a non-specific marker for DVT2,3,4 as it cannot distinguish thrombus related to spontaneous venous thromboembolism and other causes of clot formation.2 Apart from thromboembolism, elevated levels of D-Dimer may be indicative of non-thromboembolic conditions such as:
- Major surgery
- Trauma
- Sepsis
- Malignancy
- Postoperative state
- Posttraumatic state
- Infection
- Autoimmune disease
- Inflammatory disease5
- Several studies have demonstrated the high negative predictive value of the D-Dimer assay. Negative D-Dimer results are sufficient to rule-out DVT and pulmonary embolism (PE) in patients with low clinical probability.5
- With low/unlikely clinical probability and a negative D-Dimer, the need for ultrasound testing can be omitted for diagnosing DVT. However, ultrasound may be useful in establishing an alternative diagnosis.5
- Apart from thromboembolism, the D-Dimer test is used to aid in the diagnosis of disseminated intravascular coagulation (DIC).
Whom to Test
Patients with high pre-test probability of thromboembolic disease should be tested for D-Dimer levels:
- Patients with suspected PE, DVT, or aortic dissection (AD)
- Patients with chest pain or dyspnea may require D-Dimer testing to rule out PE
- Patients with acute coronary syndrome (ACS) for cardiovascular risk stratification and therapy orientation
Interpreting the D-Dimer assay results
| Clinical Category | D-Dimer Test | Interpretation |
|---|---|---|
| Low-risk patients | Negative | Imaging tests can be avoided |
| Moderate-risk patients | Negative | Venous thromboembolism can be excluded No need for imaging |
Impact on Management5
The integration strategy of combining clinical assessment with the D-Dimer assay and imaging tests enable safer, more convenient, and cost-effective patient care by enabling:
- Safe PE exclusion protocols even without imaging
- Identification of false-positive results of imaging tests
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References:
1. Hayag JE, et al. The Permanente Journal. 2006;10.
http://xnet.kp.org/permanentejournal/spring06/dimer.pdf
2. Wells PS, et al. Circulation. 1995;91:2184-87.
http://content.nejm.org/cgi/ijlink?linkType=ABST&journalCode=circulationaha&resid=91/8/2184
3. Freyburger G, et al. Thromb Haemost. 1998;79:32-37.
View source.
4. Brill-Edwards P, et al. Thromb Haemost. 1999;82:688-94.
http://www.ncbi.nlm.nih.gov/pubmed/10605769?dopt=Abstract.
5. Wells PS. J Thromb Haemost. 2007;5:41-50.
http://www3.interscience.wiley.com/cgi-bin/fulltext/117994001/PDFSTART.
